What are interrupts?

Interrupts are in some ways the mainly "famous" system resources, ever since almost everyone who's used a computer has heard of them even if they don't know what they are. An interrupt is essentially what it sounds like a message from one part of the computer to another (normally to the system processor) that tells it that it needs to stop what it is doing and perform something else instead. An IRQ is an interrupt request as well as is the name for the actual signal that is used when peripheral requests can interrupt of the processor.

Interrupts play a major role in how the processor performs input/output processing and interfaces with every peripheral in the computer from the mouse and keyboard to the hard disk and modem

The processor is a highly-tuned mechanism that is designed to (basically) do one thing at a time. Though we use our computers in a way that requires the processor to at least appear to do many things at once, if you have ever used a multitasking operating system like Windows 95, you've completed this; you may possibly have been editing a document while downloading information on your modem and listening to a CD simultaneously. The processor is capable to do this by sharing its time among the various programs it is running and the different devices that need its attention. It merely appears that the processor is doing many things at once because of the blindingly high speed that it is able to switch between tasks.